Reinforced poly(arylene sulfide) compositions are highly suitable for molding into a variety of objects which require strength, high temperature stability and chemical resistance. When carbon or glass-reinforced poly(phenylene sulfide) is molded into a large thick-walled object, such as a gas tank, internal cracking of the walls is sometimes encountered. The problem can be countered somewhat by using low melt flow, linear poly(phenylene sulfide) and is generally less pronounced with glass reinforcement than carbon reinforcement. High-density polyethylene has been used in reinforced poly(phenylene sulfide) molding compositions to improve the processability and mold release properties of the compositions. The problem of internal cracking in thick-walled parts, however, has not been consistently resolved by the addition of high-density polyethylene to the molding composition, particularly in compositions containing branched, high melt flow resin and carbon fiber reinforcement. A factor in the choice of crack-inhibiting additives is the effect of any such additive on other properties of the molding composition and of the molded article produced from the composition. The additive must not have a substantial adverse effect on the mechanical properties of the molded article and must not, as a rule, significantly decrease the flow rate of the molding composition.
It is therefore an object of the invention to provide poly(arylene sulfide) molding compositions. It is a further object of the invention to provide fiber-reinforced poly(arylene sulfide) molding compositions which can be molded into articles having improved crack resistance.